For comparison, the final of the Great British Bake-Off got the biggest viewing audience of the year so far in the UK, with more than 13 million tuning in. What’s happening now is that the rest of the mainstream is catching up.

Gambling firm Skybet quietly launched its own e-sports division last month, letting punters put money on games in League of Legends, Dota 2 and Counter-Strike: Global Offensive and BBC3, the corporation’s youth-oriented channel, has announced that it’s going to be playing its part by broadcasting the quarter finals of the League of Legends world championships live from Wembley Arena.

The channel’s controller, Damian Kavanagh, was effusive about the deal. “We jumped at the chance to collaborate with BBC Sport and bring this massive UK event to a wider audience. BBC3 will always experiment with new ways to deliver content that young people want, in ways they want. I think this is an exciting way to cover something millions of young Brits love, in a BBC3 way.”

The BBC has been somewhat quieter on the fact that the BBC3 way is to only make it available via the iPlayer, rather than on the channel’s terrestrial version, but it may figure it makes sense to start online, where the audience is already watching.

The decision was still a slightly odd announcement. The League of Legends world championships are already broadcast live to the world on Twitch, one of a small number of sites that has helped to propel this latest generation of multiplayer online games into a true spectator sport.

Even as I write this, 300,000 people are watching a group stage match on the Twitch channel of League of Legends developer Riot Games. Since the company started streaming, there have been 750m viewing sessions on that channel alone, and many many more on the personal Twitch channels of professional players and their teams.

And League of Legends is just one of many games drawing multimillion audience figures. The games that dominate the e-sports world tend to come from one particular genre: “Mobas”, short for multiplayer online battle areas. They have all the ingredients necessary for an intense spectator experience.

Simple to learn and impossible to master, mobas offer a huge amount of depth on both a strategic and tactical level, as well as requiring teammates to act together like clockwork, and offering a strong narrative arc throughout a 30-60 minute match. As well as League of Legends, there’s also Valve’s Dota 2 and Blizzard’s Heroes of the Storm as well as a number of smaller Mobas such as mobile-first game Vainglory.

All of them share a common core. Teams defend bases at opposite ends of a map, while AI minions walk down lanes towards the opposition. Hiding behind your own minions prevents the automated turrets defending bases from killing you, while taking out the enemy’s gives you resources you need to grow your character and, eventually, attack the opponent’s base directly.

While Mobas are the biggest e-sports games, they’re by no means the only ones. First-person shooters, culturally the dominant gaming genre, are well represented as well. Soldiers vs terrorists shooter Counter Strike has been the star of competitive gaming since before e-sports” was a common term, while Call of Duty in all its iterations sees big money trade hands at the highest levels. Part of the distinction is geographical: while FPS games dominate in the US, Mobas are far more popular in east Asia. Europe straddles the two.

But for almost any competitive game, there will be an e-sports audience of some size. Beat-em-ups such as Street Fighter and Super Smash Bros have a dedicated audience of their own; so too do sports sims, racing games (both hardcore sims such as Gran Turisimo and casual karting games such as Mario Kart), and tabletop style games including Hearthstone (which is having its own world tournament next month in Anaheim, with a $100,000 grand prize).

And there’s one thing that all of these scenes have in common: they’ve grown up with almost no input from the mainstream. When outsiders have turned their attention to it, the long-term effect has been mostly to galvanise entry to the same communities that already existed.

In less than five years, Twitch has grown to reach 100m viewers a month. That’s the sort of size where an attempt to steal some of those viewers for the mainstream ends up doing the opposite: introducing more viewers to the existence of a sizeable platform where they can go to be with like-minded people.

Not that this will stop media organisations trying. A potential audience of more than a hundred million people, largely from a desirable demographic which is switching off mainstream media in ever greater numbers, is too much to turn down. The mainstream is coming for e-sports. But will e-sports care?